PCM-2 Manual.pdf - Voss Associates

without screws. A silicone rubber gasket provides the gas seal between the inner
pan and mylar window/faceplate. Re-usable quick-release clips mount the
faceplate to the detector body. This screwless, gasketed design also eliminates
any face-mounting flanges so that separation between adjacent detectors is further
minimized and allows for quick and easy rebuilding of detectors with damaged
mylar windows without the need for any disposable assembly materials such as
double sticky tape.
Each detector in the standard PCM-2 unit, with the exception of the bottom foot
detector, is protected by a rugged plated steel screen with 66 % open area.
Optional thin "high sensitivity" etched (.010 thick, stainless steel, 83 % open area)
detector screens are also available. These optional screens, being physically
thinner and having a 20 % greater open area, provide a proportionate decrease in
typical measurement count times and are thereby recommended for usage in
monitoring environments where maximum sensitivity (such as alpha measurement)
is desired. The bottom foot detector rests on height adjustable brackets beneath a
rugged stainless steel slotted baseplate with 74 % open area. Because this standard
slotted baseplate design maximizes open area of detection it supports users with
relatively broad and flat soled shoes only. An optional perforated grid stainless
steel baseplate with 1/4" diameter holes (58 % open area) is available in support of
users with high-heeled shoes. Reference the Options Section for more detailed
information on these and other options.
Detector Design Configuration
PCM-2 detector assemblies have undergone design revision since the instrument
first went into production. The original detector design was based on a universal
internal anode wire support system requiring individual dielectric standoffs and
soldered wire supports. This design, although quite functional when built and
tested, has proven to be problematic from a mass production assembly standpoint.
It has, therefore, been replaced by a more readily producible design requiring
fewer internal components and assembly considerations. Both detector assembly
configurations feature identical detection capabilities and performances and are
indistinguishable in their fully assembled conditions. Identification of these
original and revised detector assemblies is possible by PCM-2 unit serialization as
follows:
Detector
Part No.
Detector Description
PCM-2 Serial No.
Effectivity
YPl1534245 Detector Assembly, Long Serial No.'s 001 tl1m
YPl1534246 Detector Assembly, Medium
150
YPl1534247
Detector Assembly, Small
16-2
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